1. Field of the Invention
The present invention relates to a method and an apparatus for manufacturing a coil-shaped continuous element row applied to a slide fastener, and more particularly to a rational and productive method and an apparatus for manufacturing a continuous coil-shaped element row, which are suitable for sequential bending and forming of upper leg portions of a large number of element units to have steps by pressing and deforming, the element units comprising coupling heads and upper and lower leg portions connected through joint portions.
2. Description of the Related Art
Each element unit (herein after, referred to as "element") of a slide fastener continuous element row manufactured by turning a monofilament made of synthetic resin into a coil shape comprises a coupling head extending perpendicularly to the element row and upper and lower leg portions extending from end portions of the coupling head in a width direction of a fastener tape and the upper and lower leg portions of the adjacent elements are coupled through a joint portion to form the continuous element row.
There are various shapes of a ring-shaped element when the element row is cut at the joint portion and viewed from a side. FIGS. 9 to 12 show the representative shapes. FIG. 9 shows an extremely common shape, i.e., so called "an egg shape". A core thread 2' may be inserted through an inside space of the egg shape in an element row direction. FIG. 10 shows an element shape wherein upper and lower leg portions L'-1 and L'-2 are close to each other such that a space between the upper and lower leg portions L'-1 and L'-2 is extremely small and that the upper and lower leg portions L'-1 and L'-2 are almost in contact with each other. Such an element row is used especially for thin outerwear and underwear. FIG. 11 shows a shape co-called "a tennis racket type" wherein portions of the upper and lower leg portions L'-1 and L'-2 close to the coupling head H' bulge outward and portions of both the leg portions L'-1 and L'-2 close to the joint portion J' are pressed such that there is almost no space therebetween. With regard to the continuous element row comprising spiral elements in such a shape, the core thread 2' may be inserted through a hollow portion of the element row.
An element shape shown in FIG. 12 is a modification of the above "tennis racket types". In other words, the lower leg portion L'-2 of the element E' extends substantially straight from the coupling head H' and the upper leg portion L'-1 is bent and deformed to be stepped at some midpoint thereof so as to be closer to the lower leg portion L'-2. Because of such a shape, a sewing yarn is disposed in an area of an upper face the upper leg portion L'-1 of each the element E', the area extending from the stepped portion toward the joint portion J', when the fastener element row is sewn on a longitudinal edge portion of the fastener tape. As a result, the sewing yarn does not project from a surface of the fastener element row and is prevented from being damaged due to its contact with other member in use of the slide fastener. Also in opening and closing operations of the slide fastener by a slider, it is possible to prevent wear in the sewing yarn due to the sliding movement of the slider and to prevent the fastener element row from falling off the fastener tape. On the other hand, because the lower leg portion L'-2 which is in contact with a surface of the fastener tape is substantially straight, the element can be fixed with the entire lower leg portion L'-2 in close contact with the fastener tape. As a result, necessary securing strength can be easily obtained and a fixed attitude of the element is stabilized.
Coil-shaped element rows in a form of the "tennis racket type" shown in FIG. 11 and in a modified form of the "tennis racket type" shown in FIG. 12 are manufactured by methods disclosed in Japanese Utility Model Publication No. 42-14901, Japanese Patent Publication No. 54-20895, Japanese Patent Publication No. 49-23874, and the like, for example.
According to the Japanese Utility Model Publication No. 42-14901, a continuous monofilament is spirally wound around a mandrel, the wound monofilament is transferred by a pair of screws which face each other with the mandrel being disposed therebetween, and at the same time, portions of the monofilament corresponding to the upper and lower leg portions are pressed by bottom faces of spiral grooves of the pair of screws into a narrowed shape. In other words, each the element is in the form of the "tennis racket type" wherein the upper and lower leg portions gradually approaches each other toward the joint portion.
The element form disclosed in the above Japanese Patent Publication No. 54-20895 and Japanese Patent Publication No. 49-23874 is a modification of the above "tennis racket type" shown in FIG. 11. Especially in the Japanese Patent Publication No. 49-23874, a continuous monofilament is spirally wound around a mandrel, the wound monofilament is pressed by one of a pair of pressing rollers which face each other with the mandrel being disposed therebetween to form coupling heads, and a portion of the upper leg portion near the joint portion is pressed in a narrowed shape toward the lower leg portion by the other of the pressing rollers to form a stepped portion, thereby bending and forming the upper leg portion into a stepped shape.
Therefore, according to the above Japanese Utility Model Publication No. 42-14901, the continuous element row is formed to have configuration as described above. Therefore, in order to reliably press and deform the portions to be upper and lower leg portions of the coil-shaped monofilament spirally wound around the mandrel into the narrowed shape by the bottom faces of the pair of opposed spiral grooves, a complicated cutting process such as for making a shape of a bottom face (groove depth) of the spiral grooves of the screws which gradually shallow is required.
On the other hand, according to the method for manufacturing the fastener element row disclosed in the Patent Publication No. 54-20895, the coupling head and the upper leg portion of each the element wound around the mandrel are pressed and deformed by the pair of pressing rollers. Because the pressing of the fastener element row is only carried out by the rotary rollers, the elements carried on the mandrel are subject to a sliding resistance of the mandrel and variation in pressing force of each the roller and a pitch of the elements is liable to be varied.